1. Field of the Invention
The present invention relates to a current sensor that measures current flowing through a current path, based on a magnetic field near the current path.
2. Description of the Related Art
There is known as related art a current sensor that is arranged in a measurement-subject current path, measurement-subject current flowing through the measurement-subject current path, detects a magnetic field generated by the measurement-subject current flowing through the measurement-subject current path, and detects current flowing through the current path based on the detected magnetic field. Such a current sensor is mounted, for example, on a three-phase motor including three current paths arranged so that extending directions of the current paths are parallel to one another. The current sensor mounted on the three-phase motor has to restrict the effect of the magnetic field generated by the current flowing through a current path (a neighboring current path) provided next to the measurement-subject current path and prevent measurement accuracy for the measurement-subject current from being decreased. As a method of restricting the effect of the magnetic field caused by the neighboring current path, for example, there is suggested a current sensor illustrated in FIG. 10 that a pair of magnetoelectric conversion elements measure a magnetic field generated by measurement-subject current, and a magnetic field generated by current flowing through a neighboring current path is similarly applied to the magnetoelectric conversion elements. With this current sensor, the magnetic field generated by the measurement-subject current is applied to the pair of magnetoelectric conversion elements in the opposite directions, and the magnetic field generated by the neighboring current is applied to the pair of magnetoelectric conversion elements in the same direction. Hence, by using a difference between outputs of the pair of magnetoelectric conversion elements, the magnetic field generated by the neighboring current can be canceled. Also, an external magnetic field such as geomagnetism is applied to the pair of magnetoelectric conversion elements in the same direction, and hence the magnetic field can be canceled (for example, see Japanese Unexamined Patent Application Publication No. 2010-266290).
However, in the case of the current sensor disclosed in Japanese Unexamined Patent Application Publication No. 2010-266290, the magnetic field generated by the current flowing through the neighboring current path is superposed on the magnetic field generated by the current flowing through the measurement-subject current path in the same direction. Therefore, each of the magnetoelectric conversion elements should be able to measure the magnetic field having a strength with both magnetic fields added. Accordingly, the dynamic range is decreased by the amount corresponding to the strength of the magnetic field generated by the current flowing through the neighboring path.